djb

Tubus racks are great racks, I got a front and rear for a bike to be used for long trips, and am glad I did---but now we come to the "but"

but, I have also used good quality aluminum racks for decades and decades, and commute nearly daily using these reasonably priced, but well built enough racks, and yes the paint rubs off a bit, but they work perfectly fine.

in both my opinion and experience, a good quality alu rack is perfectly good--especially if you aren't loading the heck out of it, which on your gravel bike, is probably not the case.

but for your specific question, yes tubus racks can have paint scuffed off and surface rust happen--but I put tape on the contact points to minimize this, and have touched up tiny spots with regular old black metal paint I have around for doing my house porch railings.

do you need a steel Tubus rack, most likely not.
just know that good alu racks work fine, at easily half the cost or less.

oh, the aluminum "Racktime" racks are well made, we used one for a while and it is a good solid rack, but there are many well established similar alu rack brands out there. Don't go for a cheapie imo.